DESCRIPTION: (Investigator's Abstract): The proposed research will determine the patterns of cell proliferation, migration and dispersion of a defined region of the developing murine cerebral cortex, the dorsomedial sector of the E13-E17 cerebral wall. Patterns of cell generation will be determined for the total population of the VZ and SVZ by the method of cumulative labeling with BUdR. Patterns of generation of the "indifferent" population as well as cells of the astroglial lineage will be discriminated by staining with the cellular antigen marker for radial glial cells, RC2. Parameters of cell production will be based upon the output pattern of a 1 hour cohort of S-phase cells, identified by 3H-thymidine pulse labeling, and followed in 1 hour by a cumulative labeling with BUdR to reveal the total population. The patterns of clonal output and of clonal dispersion will be corroborated by labeling with retroviral transfer of xgal at E12.